Escherichia coli is a common enteric bacterial strain that has both laboratory and human health importance. One particular strain of E. coli designated O157:H7 is a human enteric pathogen that causes acute hemorrhagic colitis. Young children and the elderly are particularly susceptible to disease caused by this bacteria, which is usually contracted by eating contaminated food such as undercooked meat. In the most vulnerable patients, the colitis frequently develops into hemolytic uremic syndrome (HUS), a condition that is often fatal. The disease has a very rapid progression, and is consequently very difficult to treat. Often, patients are severely ill by the time the disease is diagnosed. Once a diagnosis has been made, appropriate antibiotics may be administered to kill the infective bacteria. Sometimes, however, by the time a diagnosis has been rendered, toxic proteins secreted by the bacteria have damaged mucosal cells and entered the blood stream. Recently, clinical isolates of O157:H7 have been found to exhibit resistance to an increasing spectrum of antibiotics, which will further complicate treatment.
The source of the bacteria in the several recent cases of disease caused by this organism were traced to hamburgers purchased in fast food restaurants. The bacteria are extremely proficient at establishing an infection; ingestion of as few as 10 live bacteria is sufficient to establish an infection. The highly infective nature of O157:H7 and the devastating sequelae associated with infection by this bacteria, together with the extensive public attention given to outbreaks of hemorrhagic colitis, has generated a great deal of interest among medical professionals and the general public in developing the means for early diagnosis and treatment of the disease. Farmers are desirous of an effective treatment of infections in cattle and pigs, which are the main reservoirs for E. coli enteric pathogens. The ability to diagnose and treat livestock infected by this organism will prevent the loss of livestock and the transmission of the organism from animals to humans. Meat suppliers and those in the food industry are very much interested in a means for detecting the organism in tainted meat. Because the infective dose of O157:H7 is extremely low, a highly sensitive test is needed to identify contaminating organisms in food.
Modern geneticists have been working to resolve the genetic code of many organisms. Efforts to sequence the human genome are ongoing. The effort to sequence the genomes of whole organisms began with an effort to sequence the genome of E. coli. For the original effort to sequence the E. coli genome, a useful and common laboratory strain, designated K12, was chosen. The entire genome of that strain was sequenced and published. Science, 277:1453-1462 (1997). Since the genes which are responsible for the pathogenicity of E. coli 0157:H7 are missing from strain K12, the sequence of the K12 genome is of limited help in developing tools to detect, hinder or destroy E. coli 0157:H7.
Some efforts have been directed toward the sequencing of specific genes from 0157:H7. U.S. Pat. No. 5,798,260 describes the sequence of one specific gene, named adhesion, from that genome. The development of additional sequence information from E. coli 0157:H7 would be needed for comprehensive efforts at detection, diagnosis, prophylaxis and therapeutic approaches to infections caused by the organism.